Warning about installing DragonFly and FreeBSD to same disk

Here's something I found out the hard way last night:
If you already have DragonFly on a disk (say partition 1) and you want
to install FreeBSD on that disk (say partition 2), you have to be very
careful.
Because DragonFly and FreeBSD have the same partition id (165,)
FreeBSD's installer will see the DragonFly partition as a FreeBSD slice.
And, *even if you don't set up any BSD partitions on the DragonFly
partition*, the installer will erase the DragonFly partition's
disklabel.
I haven't tested any workarounds yet, but I suspect that marking the
DragonFly partition with some other partition id (like MS-DOS) before
installing, and marking it back after installing, would be enough to
trick FreeBSD's installer into ignoring it.
-Chris